Oregon Vaccine Hesitancy Index PPT

5/21/2018 Oregon Vaccine Hesitancy Index PPT

1/19

Development of a

Measure of VaccineHesitancy

Steve Robison, James Gaudino,Martha Priedeman Skiles,

Collette Young

Immunization Program,

Office of Family Health,

Oregon DHS

NIC 2008


2/19

Oregon Background

Belief-based exemptions to

school requirements are allowed

in Oregon and are increasing.

Many exemptions in Oregon aregeographically clustered.

Parents in Oregon communities

with high exemption ratesappear to have serious doubts

about immunizations.

???


3/19

Vaccine

Hesitancy -

Vaccine hesitancy can lead to parents avoiding

some or all of the early childhood immunizations

or to later sign exemptions to school requirements. Obtaining medical or school records for evidence

of hesitancy can be difficult or expensive.

a term to describe increasing

parental worries about

immunizations.


4/19

Purpose

To develop an

attitudinal measure of

hesitancy based on

data including

exemptions; and

To test the measuresutility in identifying

vaccine hesitant

populations


5/19

Oregon Parental Exemption Survey

Multi-stage, cluster survey with a population-

proportionate sample of Oregon households, 2006

Case-control sample matched by school and grade;

1exemptor : 3non-exemptor

Mail, phone and internet survey of parents

immunization attitudes and practices;

Overall response rates of 54%, with a 48%

response rate among exemptors; N=1,592

Weighted in STATA to reflect Oregon population.


6/19

Vaccine Attitude Questions

*Asked on a 5- point Likert scale, %=Agree somewhat to strongly

Question Agree*

It is important for kids to get all doctor

recommended shots

Vaccines are given at too young an age

The benefits of childhood vaccinations

outweigh their risks

Getting too many vaccines at once will

overwhelm my childs immune system

It is better for my child to get diseases

naturally

31.8%

87.1%

19.3%

19.5%

82.1%

10.5%

Vaccines sometimes cause autism


7/19

Oregon Vaccine Hesitancy Index

The OVHI was created by combining the six

attitudinal measures by the following:

The scales on all six items were set in the same

direction, from least to most hesitant;The scores for all items were added, then

normalized to a interval from zero to one.

Missing values were coded at the midpoint Resulting index had a Cronbachs alpha of .84,

supporting the assumption of an underlying

dimension of hesitancy


8/19

OVHI & Exemptions

The first check on the utility of the index is its

relation to exemptions.

Exemption Status by OVHI ScoreOVHI Mean 95% CI

Exemptor 0.613 0.541 to 0.683

Considered 0.461 0.433 to 0.487

Vaccinated 0.262 0.252 to 0.270

Considered = parents who reportedly considered signing an

exemption but instead chose to vaccinate


9/19

OVHI & Other Measures

The OVHI can also be contrasted to other

items of relevance to immunization:

Social closeness to perceived vaccine harm

Getting shots for another baby


10/19

Social Closeness to Harm

Parents were asked if:

they knew about children hurt by vaccines,

they had read or heard about hurt children, and

they knew someone with an allegedly hurt child,

including their own.

The closer the source of any alleged harm, the moreimpact it is likely to have on vaccination attitudes

and decisions.


11/19

OVHI and Perceived Harm

As expected, an increased closeness of perceived

harm is associated with increased hesitancy.

Social Closeness OVHI Mean 95% CI

No Knowledge 0.247 .229 to .264

Distant(heard or read) 0.291 .274 to .308Close(know someone 0.445 .413 to .477

Own Child 0.514 .440 to .589


12/19

Willingness to Get Shots

Today for Another BabyAnother possible

dependent variable for

analysis on the survey isan item used by Gust et

al*. This item asks

parents if they would get

all recommended shotsfor another baby today.

*Pediatrics v114:1, July 2004.


13/19

Shots for Another Baby

Would Get All Shots for Baby Today?

OVHI Mean 95% CI

Yes 0.257 .249 to .265

No 0.534 .504 to .565

Parents with doubts about getting all

shots now also had significantly higher

hesitancy levels.


14/19

Using the OVHI

For Screening

The OVHI can be used as

a predictive screening toolto identify groups withexemptions or otherimmunization concerns.

survey tool client tool


15/19

OVHI & Exemptions (2)OVHI Compared to Survey Exemptions

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

OVHI breakpoint

sensitivity

specificity

Sensitivity = ability to correctly identify ALL cases (or exemptors)Specificity = ability to identify ONLY TRUE cases (or exemptors)


16/19

Using the OVHI to Select Groups

Often interest in public health is not with the most

hesitant group, but with those who are still fence-

sitters - likely to sway one way or another andtherefore more amendable to intervention.

Three hesitancy groups created from OVHI:

Mostly Accepting (OVHI under .5)

Fence-Sitting (OVHI between .5 and .75)

Vaccine-Resistant (OVHI over .75)


17/19

OHVI Survey Frequencies

0

50

100

150

0 .2 .4 .6 .8 1

OVHI

Vaccine

Resistant

(3%)

Fence

Sitters

(15%)

Mostly

Accepting

(82%)


18/19

Hesitancy Groups & Exemptions

Hesitancy Index Vaccinated Considered Exempt

Mostly Accepting 71.7% 26.0% 2.3%

Fence Sitters 15.4% 39.5% 45.1%

Vax Resistant 2.2% 9.2% 88.6%

Total 79.4% 14.3% 6.3%

Exemption Status

Considered = parents who reportedly considered signing an

exemption but instead chose to vaccinate


19/19

Conclusions

The Oregon VaccineHesitancy Index

(OVHI) is potentially a

useful tool for

screening populationsfor vaccine issues to

identify groups for

interventions.

Next Steps - use in a population survey or in a

clinical setting as a screening tool for parents who

may need further information.

Oregon Vaccine Hesitancy Index PPT

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